The general objective of this project is to study the effects of trace elements upon spermiogenesis in mammals, with emphasis in the near future upon the involvement of two trace elements, zinc and selenium, in the formation and organization of specialized tail structures whose unusual stability is conferred by half-cystine bridges. The species employed for the proposed studies will be rats and mice. These investigations will seek to extend present knowledge concerning the identity of the testicular cells, organelles and proteins which take up zinc and selenium, the timing of their respective incorporations, and the effects of their respective deficiencies upon spermiogenesis. Relative distributions of cysteine and selenocysteine in a specific polypeptide of outer mitochondrial membranes will be examined as a function of germ cell maturity. The ability of immature and mature Sertoli cells to take up zinc and selenium and the effects of FSH upon such incorporation will be assessed in cell cultures. Finally, preliminary studies will be conducted bearing upon the possibility that glutathione interacts critically with cysteine-rich problems and one or more trace elements during spermiogenesis.